Saul Kivimäe, Takahiro Miyazaki, Rhoneil Pena, Marlene Hennessy, Wildaliz Nieves, Andrew Moffett, Phi Quach, Mekhala Maiti, Lawrence Chinn, Loui Madakamutil and Jonathan ZalevskyNektar Therapeutics, San Francisco, CA

NKTR-255, a polymer-conjugated IL-15 receptor agonist, enhances efficacy of therapeutic monoclonal antibodies with ADCC activity in solid tumor models

Poster # P619

Introduction Results

Results

References

Conclusions

• IL-15 is a critical cytokine for NK cell survival and functional activation. Therapeutic application of native IL-15 has been challenging due to unfavorable pharmacokinetic properties and tolerability.

• NKTR-255 is a polymer conjugated human IL-15 that retains binding af�nity to the IL-15 receptor alpha subunit and exhibits reduced clearance to provide a sustained pharmacodynamic response including proliferation and functional activation of NK cells.1

• NKTR-255 has potential to increase ef�cacy of tumor targeting antibody therapies with ADCC mechanism of action by expanding NK cells with increased cytotoxicity and enhanced surface expression of low af�nity Fc receptor CD16.

• We have previously demonstrated ADCC enhancement by NKTR-255 with daratumumab and rituximab in B cell lymphoma xenograft tumor models1. Here we extend this therapeutic concept into solid tumor setting showing NKTR-255 dependent enhancement of ADCC in vitro with colorectal and head and neck squamous cell carcinoma (HNSCC) tumor cell lines and improvement of cetuximab and trastuzumab ef�cacy in vivo correlating with proliferation and functional activation of tumor resident NK cells in multiple xenograft solid tumor models in mice.

ADCC is a crucial mechanism in tumor depletion by tumor-targeted antibodies. CD16 Fc receptors on NK cells recognize tumor cell-bound antibodies and the CD16 engagement triggers release of cytotoxic granules and cytokines to kill tumor cells. IL-15 enhances NK-mediated ADCC.2

Balb/c nude mice (n=10/group) bearing subcutaneous NCI-N87 or SKOV-3 xenograft tumors were treated IV with NKTR-255 and trastuzumab at indicated doses starting treatment at mean tumor volume of ~150mm3. Relative tumor volumes normalized to starting tumor size were graphed to quantify tumor growth inhibition (TGI) by treatments (*, p<0.05 relative to vehicle, one-way ANOVA; SEM – standard error of the mean).

Balb/c SCID mice (n=4/group) bearing subcutaneous HCT-116 or FaDu tumors were treated with NKTR-255 (0.3 mg/kg, IV) and cetuximab (20 mg/kg, IP) 7 days after tumor inoculation at mean tumor volume of ~150mm3. NK cells in blood and in tumors were analyzed by �ow cytometry on Day 3 and Day 5 after treatment. (*, p<0.05 relative to vehicle treatment, multiple t-test; SD – standard deviation).

Balb/c SCID mice (n=8/group) bearing subcutaneous HT-29 or HCT-116 xenograft tumors were treated with NKTR-255 (0.3 mg/kg, IV, q7dx3) and with cetuximab (40 mg/kg, IP, BIWx3) starting treatment at mean tumor volume of ~150mm3. Relative tumor volumes normalized to starting tumor size were graphed to quantify tumor growth inhibition (TGI) by treatments. Tumor growth delay (TGD) in drug treated animals was evaluated relative to vehicle treatment by measuring tumor volume quadrupling time (TVQT) indicating time to reaching 400% tumor volume (TV) growth from baseline as prede�ned survival endpoint (*, p<0.05 relative to vehicle treatment, one-way ANOVA; SEM – standard error of the mean).

Human PBMCs were cultured overnight with 100 ng/ml NKTR-255 on non-coated or 0.1 mg/ml hIgG coated plates. CD69 and CD107 expression on NK cells was measured by �ow cytometry (*, p<0.05 relative to no treatment, one-way ANOVA; SD – standard deviation).

Puri�ed human NK cells were cultured overnight with or without NKTR-255. Activated NK cells (effector cells) were co-cultured with cetuximab pre-coated FaDu (HNSCC) or HCT-116 (colorectal cancer) cells (target cells) at indicated antibody concentrations at effector:target ratio of 10 for 3 hrs at 37ºC. NK cells killing activity was evaluated by detecting 7-AAD stained target cells (*, p<0.05 relative to no treatment, #, p<0.05 relative to cetuximab single agent, one-way ANOVA; SD – standard deviation).

Antibody-dependent cellular cytotoxicity (ADCC) by NK cells

Synergistic activation and degranulation enhancement in human NK cells by NKTR-255 and CD16 Fc receptor crosslinking

NKTR-255 enhances trastuzumab tumor growth inhibition activity in human tumor xenograft models in mice

NKTR-255 combination treatment with cetuximab induces NK cell expansion and increased functional activation in blood and tumor tissue in human HNSCC and colorectal cancer xenograft tumor models in SCID mice in vivo

NKTR-255 combination treatment with cetuximab produces tumor growth inhibition activity and induces tumor growth delay in cetuximab resistant human colorectal cancer xenograft tumor models

NKTR-255 enhances cetuximab mediated NK cells ADCC against HNSCC and colorectal cancer cell lines in vitro

0

4000

8000

12000

CD69 Expression on NK Cells

MF

I (M

ean

± S

D, n

=2)

NKTR-255 - + - + - - + +IgG

*

0

1000

2000

3000

CD107 Expression on NK Cells

MFI

(Mea

n±

SD

, n=

2)

NKTR-255IgG

- + - + - - + +

*

*

0

20

40

60

% FaDu Cell Death

% C

D45

- /

7-A

AD

+(M

ean

± S

D, n

=2)

- 300 - - 300 300- - 0.3 - 0.3 -- - - 0.3 - 0.3

*

*#

#

Presented at Society for Immunotherapy of Cancer 2019 Annual Meeting

0

20

40

60

% HCT-116 Cell Death

% C

D45

- /

Ep

CA

M+

/ 7

-AA

D+

(Mea

n±

SD

, n=

2)

NKTR-255, ng/mlCetuximab, µg/ml

Isotype, µg/ml

- 300 - - 300 300

- - 30 - 30 - - - - 30 - 30

**

*

*

#

#

1. Miyazaki et al. NKTR-255, a polymer-conjugated IL-15 enhances anti-tumor NK cell responses and synergizes with monoclonal antibodies to provide long-term survival in human lymphoma model. AACR. 2019, Poster 3265.

2. Wei et al. NK cell-mediated antibody-dependent cellular cytotoxicity in cancer immunotherapy. Front Immunol. 2015; 27.

• NKTR-255/IL-15R and mAb Fc/CD16 signals in combination synergistically activate NK cells indicating ADCC therapeutic mechanism enhancement potential for NKTR-255.

• NKTR-255 enhances cetuximab-mediated killing of colorectal and HNSCC tumor cells in vitro.

• NKTR-255 induces proliferation and cytotoxic activation of NK cells in blood and in the tumor environment of colorectal and HNSCC xenograft solid tumor models in vivo.

• NKTR-255 in combination with cetuximab induces tumor growth inhibition in cetuximab single agent resistant. solid tumor xenograft models.

• NKTR-255 enhances ef�cacy of trastuzumab in solid tumor xenograft models.

• NKTR-255 has a potential to be applied with certain cancer therapies to enhance ADCC dependent therapeutic activity of tumor-targeting monoclonal antibodies in solid tumors.

0 5 10 15 20 250

100

200

300

NCI-N87 (Gastric Carcinoma)Tumor Growth Inhibition

Days after treatment start

Rel

ativ

eT

umo

rV

olu

me

(Mea

n±

SE

M,D

ay0=

100%

)

Vehicle

Trastuzumab (3/1/1 mg/kg, q7dx3)

NKTR-255 (0.3 mg/kg, q7dx3)

Trastuzumab (3/1/1 mg/kg, q7dx3) +NKTR-255 (0.3 mg/kg, q7dx3)

**

TGI = 46%TGI = 92%

0 5 10 15 20 25 300

250

500

750

1000

SKOV-3 (Ovarian Adenocarcinoma)Tumor Growth Inhibition

Days after treatment start

Rel

ativ

eT

umo

rV

olu

me

(Mea

n±

SE

M,D

ay0=

100%

)

Vehicle

Trastuzumab (13.5 mg/kg, BIWx3)

NKTR-255 (0.3 mg/kg, q7dx3)

Trastuzumab (13.5 mg/kg, BIWx3) +NKTR-255 (0.3 mg/kg, q7dx3)

35

TGI = 65%100% CR

*

*

*

Tumor Blood

Flow cytometry analysis (Day 3 and Day 5 after treatment)

HCT-116FaDu

Day 3 Day 50

10

20

30

40

IntratumoralNK Cell Fraction

% N

K c

ells

in t

ota

l liv

e ce

lls(M

ean

± S

D) * *

Day 3 Day 5104

105

106

IntratumoralNK Cell Count

Cel

l nu

mb

ers

(Mea

n±

SD

)

**

Blood Tumor0

25

50

75

100

NK CellProliferation

% K

i67+

(Mea

n±

SD

)

* *

Blood Tumor0

25

50

75

100

GzmB Expressionin NK Cells

% G

zmB

+ (M

ean

± S

D) * *

(Day 3) (Day 3)

FaDu

Blood Tumor0

500

1000

1500

CD16 Cell Surface Expression on NK Cells

MF

I (M

ean

± S

D)

*

Blood Tumor0

5

10

15

NKG2D Expressionon NK Cells

% N

KG

2D+

(Mea

n±

SD

)

Vehicle

NKTR-255 +Cetuximab

*

*

(Day 3) (Day 3)

Day 3 Day 50

5

10

15

IntratumoralNK Cell Fraction

% N

K c

ells

in t

ota

l liv

e ce

lls(M

ean

± S

D)

*

*

Day 3 Day 5104

105

106

IntratumoralNK Cell Count

Cel

l nu

mb

ers

(Mea

n±

SD

)

*

Blood Tumor0

25

50

75

100

NK CellProliferation

% K

i67+

(Mea

n±

SD

)

* *

Blood Tumor0

25

50

75

100

GzmB Expressionin NK Cells

% G

zmB

+ (M

ean

± S

D) * *

Blood Tumor

500

1500

2500

3500

CD16 Cell Surface Expression on NK Cells

MF

I (M

ean

± S

D)

*

*

Blood Tumor0

5

10

15

20

NKG2D Expressionon NK Cells

% N

KG

2D+

(Mea

n±

SD

)

Vehicle

NKTR-255 +Cetuximab

*

*

(Day 3) (Day 3) (Day 3) (Day 3)

HCT-116

0 5 10 150

200

400

600

800

1000

HCT-116 (Colorectal Carcinoma)Tumor Growth Inhibition

Days after treatment start

Rel

ativ

eT

umo

rV

olu

me

(Mea

n±

SE

M,D

ay0=

100%

)

19

**

TGI = 35%TGI = 48%

0

25

50

75

100

HCT-116 (Colorectal Carcinoma)Tumor Growth Delay (TVQT)

Days after treatment start

% S

urvi

val

(End

po

int

=40

0%T

V) **

5 10 2015

TGD = 26%TGD = 42%

0

200

400

600

800

HT-29 (Colorectal Carcinoma)Tumor Growth Inhibition

Days after treatment start

Rel

ativ

eT

umo

rV

olu

me

(Mea

n±

SE

M,D

ay0=

100%

)

*

0 5 10 15 21

TGI = 43%

0

25

50

75

100

10 15 20

HT-29 (Colorectal Carcinoma)Tumor Growth Delay (TVQT)

Days after treatment start

% S

urvi

val

(End

po

int

=40

0%T

V)

Vehicle

Cetuximab

NKTR-255

Cetuximab +NKTR-255

23

*

TGD = 38%NKcell

CD16 Fc receptor

IL-15Rs

NKTR-255

Co-culture assay

NKTR-255 primedhuman NK cells

Cetuximab pre-coatedtarget cells

Targetcell

Cetuximab

EGFR

C

M

Y

CM

MY

CY

CMY

K

SITC2019 NKTR-255 Kivimae poster d2 for print.pdf 1 10/31/2019 9:44:32 AM